ASoC: Add a shutdown callback

Ensure that the audio subsystem is powered down cleanly when the system
shuts down by providing a shutdown operation. This ensures that all the
components have been returned to an off state cleanly which should avoid
audio issues from partially charged capacitors or noise on digital inputs
if the system is restarted quickly.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Tested-by: Ben Dooks <ben-linux@fluff.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 653435930ad..b9129efeedf 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -2032,6 +2032,35 @@ void snd_soc_dapm_free(struct snd_soc_device *socdev)
 }
 EXPORT_SYMBOL_GPL(snd_soc_dapm_free);
 
+/*
+ * snd_soc_dapm_shutdown - callback for system shutdown
+ */
+void snd_soc_dapm_shutdown(struct snd_soc_device *socdev)
+{
+	struct snd_soc_codec *codec = socdev->card->codec;
+	struct snd_soc_dapm_widget *w;
+	LIST_HEAD(down_list);
+	int powerdown = 0;
+
+	list_for_each_entry(w, &codec->dapm_widgets, list) {
+		if (w->power) {
+			dapm_seq_insert(w, &down_list, dapm_down_seq);
+			powerdown = 1;
+		}
+	}
+
+	/* If there were no widgets to power down we're already in
+	 * standby.
+	 */
+	if (powerdown) {
+		snd_soc_dapm_set_bias_level(socdev, SND_SOC_BIAS_PREPARE);
+		dapm_seq_run(codec, &down_list, 0, dapm_down_seq);
+		snd_soc_dapm_set_bias_level(socdev, SND_SOC_BIAS_STANDBY);
+	}
+
+	snd_soc_dapm_set_bias_level(socdev, SND_SOC_BIAS_OFF);
+}
+
 /* Module information */
 MODULE_AUTHOR("Liam Girdwood, lrg@slimlogic.co.uk");
 MODULE_DESCRIPTION("Dynamic Audio Power Management core for ALSA SoC");